A new, stable trimeric TNFα structure is disclosed with distorted symmetry which can bind to the TNFR1 receptor to attenuate signalling therefrom, which can be used in the treatment and/or prevention of diseases associated with the soluble TNFα/TNFR1 interaction. Membrane-bound TNFα is not affected in its ability to signal through TNFR2, and thus the new structure of TNFα may be used in therapies which do not significantly raise the risk of infection or malignancy.